An elevation is different. It shows the face of something, or perhaps more correct, the projection of an object/s to a plane. But my testing suggests it produces SECTIONS, not elevations.
Yes, you can use abbreviations in tables and figures. All abbreviations used in tables and figures should be defined in the table note or figure caption, respectively, even though the abbreviations will be also be defined in the text if they are used there.
In standard formal English, they are spelled out. If you spell out the number, spell out the unit of measurement. There is no need to add an s to an abbreviation to show a plural. This is sometimes done in advertising (3 lbs. for a dollar), but it is not necessary. English Unit Abbreviations. The single hatch mark ' can stand for foot or a geographical minute (a minute of longitude or latitude).